Impeller



A. GARVE Nov. 4, 1941.

IMPELLER Filed Oct. 22, 1938 Wjw ,9. Q 2 PM Patented Nov. 4, 1941 UNlTED STATES PATENT. OFFICE 2,261,463 I V A WELLER Alexander Garve, Augsburg, Germany. assignor to Maschineniabrik Augsburg-Niirnberg A. G., v Augsburg, Germany, a corporation of Germany Application October 22, 1938, Serial No. 236,521 a In Germany October 19, 1937 4 Claims.

This'invention relates to air or gas compressors;

One object of the invention is the provision of a compressor such as may be used for compressingalr or combustible mixture for charging the cylinders of aircraft engines and the like,'the compr'essor'having a rotatable member provided with radial blades forming impelling passages that extend substantially axially at their inlet prevent excessive blade friction losses butsuf ficient to provide a moderate angle between adjacent blades, the width of the blade passages measured in an axial plane decreasing towards the outlet ends at such rate that the inclination of a line connecting points plotting the passage width at the inlet and outlet ends of the passage against the distance along the passage is at an angle of 19 or more to the base line on which the distance along the passagels measured.

Another object of the invention is the pro: vision of an impeller of the character mentioned in which the cross sectional area at the outlet end of a blade passage is less than 65% of the.

cross sectional area of the blade passage at the inlet end thereof.

' Another object of the invention is the provision of an impeller of the character mentioned in which the ends of the blades are convexly curved on the leading side of the blade in accordance with the direction of flow discharge from the blade, while the rear side ofthe blade is substantially straight.

Other objects and advantages of the invention will be apparent from the following description, the appended claims and the accompanying drawing, in which:

Fig. 1 is an axial sectional view through the upper half of an impeller embodying the present invention; a

Fig. 2 is a side view or a portion of the impeller;

and

Fig. 3 is a diagrammaticshowing of the channel width with relation to difierent mean distances along the channelpassa'ges.

In accordance with the present invention Figs.

impeller, the casing extending along and closing one side of the passages in the impeller and providing a substantially axial inlet. The passages provided between the adjacent blades are suitably curved and streamlined to gradually change the direction of flow of the medium handled from v a generally axial direction to a generally radial direction. The gaseous medium such as air or combustion mixture compressed by the impeller may be employed for charging thecylinders of aircraft engines, the impeller of the present invention being particularly adaptable for use with a fluid pressure turbine drive.

The impeller is provided with a series of blades which extend substantially radially. As herein shown, the blades of an impeller are twelv in or gas in the channel is effectively propelled as the air or gas travels along. the passage. As

1 and 2 show portions or a rotatable impeller number so that the number of blades will not be so high as to create excessive friction losses due to the friction of the air or gas acted upon, and will not be so small as to present a disadvantage of a large angle of divergence between adjacent blades such as would decrease the rate of flow and the air pressure of the delivered air or gas because of an excessive rate of increase in the passage dimensions measured circumferentially.

The width across each passage measured in an axial plane diminishes towards the outlet end of the passage at a considerably greater rate than has been customary so as to maintain air or gas pressure against the rear sides of the blades during its flow from inlet to outlet. "Thus the air shown inFig. 3 the passage widths at diflerent distances along the mean or n eridinal line m of the passage are shown plotted against the distance along the passage. In this figure, the

channel width at the points A and B of Fig. 1 are represented by the height of the lines a-A and bB- respectively while the distance :between the points A and B in Fig. 3 is the lineal distance of the mean dot and dash line m ofthe passage. The dotted line in 3 shows the actual passage widths in the construction herein shown, in which the passage width is maintained substantially constant immediately adjacent the inlet end, and-then starts to decrease in width at the point C in Fig. 1. Fig. 1 shows the difier-- ent diameters of the several circles whose centers are arranged at spaced intervals along the mean I is a measure of the rate of decrease of the passage width from the inlet end to the outlet end of the passage, and the inclination of this line in accordance with the present invention is 19 or more to the base line AB on which the dis-- tance along the passage is measured in order that thepassage will be maintained full of the gaseous medium and a pressure will be maintained on the rear sides or the blades as the gas travels along the passage to the outlet end thereof. As shown in Fig. 3, the angle :11 between the points a and b is somewhat in excess of 19. Since the taper of the passage in the form of construction illustrated does not start exactly at the inlet end but rather at the point C, the taper of the passage between the points and b in Fig. 3 must be at an angle of a: which is in excess of 22.

It is a further feature of the invention that the cross sectional area at the inlet end of the passage should be greatly in excess of the cross sectional area through the entire passage at the discharge end thereof, the outlet cross sectional area being smaller than 65% of the inlet cross sectional area of the passage.

As will now be apparent, although the number of blades is neither excessively large nor excessively small, and although the distance between the blades increases in an outward direction, the cross sectional area of the passage provided between adjacent blades decreases in an outward direction and at such a rate that the pressure and impelling eflect of the blades is maintained on the gas during its flow through the passages. Where the width of the passage decreases towards the outlet end at such a rate that the inclination of a line plotting the width at the inlet and outlet ends of the passage against the dis-.

tance along the passage is at an angle of 19 or more to the base line on which the distance along the passage is measured, there will result a very considerable increase in the quantity of air or gas delivered, an increase in the delivered pressure and in the eficiency.

In order to further prevent any decrease in the pressure of the gas or air in the passage at the ends of the passages, the ends of the blades are convexly curved on their front sides at their tip portions so as to conform substantially to the direction ofdischarge flow, and the gas or air leaving the compressor blades may depart from the blades without abruptly changing their direction, the rear sides of the blades extending substantially straight or radially so as to maintain their effectiveness to the end of the passages.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which line connecting points plotting the passage width 19 or more to the base line on which the distance along the passage is measured to maintain an eflective propelling action on the medium flowing through the passages.

2. A rotatable impeller wheel of the character described for handling a gaseous medium comprising a wheel having a series of substantially radial blades diverging at an angle of the order of 30 to one another and providing impeller passages extending substantially axially at their tance adjacent the inlet end and then decreasing toward the outlet end of the passage at such rate that the inclination of a line plotting the passage width of the tapered portion of the passage at different distances along the meridian line of the passage is at an angle of 22 or more to the base line on which the distances along the passage are measured to maintain an efiective propelling action on the medium flowing through, the passages.

3. A rotatable impeller wheel of the character described for handling a gaseous medium com-; prising a wheel having a series of substantially radial blades diverging at an angle of the order of 30 to one another and providing impeller passages extending substantially axially at their inlet ends and radially at their outlet ends, the

width of the passages measured in an axial plane decreasing towards the outlet ends at such rate that the inclination of a line connecting points plotting the passage width at the inlet and outlet ends of the passage against the distance along the passage is of an angle of 19 or more to the base line on which the distance along the passage is measured so as to maintain a pressure of the gaseous medium against the rear sides of the blades as the gas travels along the passage, the outer ends of the blades having a convex form on the leading sides thereof while the rear side of the blade is substantially straight.

- 4. A rotatable impeller wheel of the character described for handling a gaseous medium comprising a wheel having a series of substantially radial blades diverging at an angle of the order of 30 to one another and providing impeller passages extending substantially axially at their inlet ends and radially at their outlet ends, the width of the passages measured in an axial plane being substantially constant for a limited distance adjacent the inlet end and then decreasing toward the outlet end of the passage at such rate that the inclination of a line plotting the passage width of the tapered portion of the passage at difierent distances along the meridian of the passage is at an angle of 22 or more to the base line on which the distance along the passage is measured whereby the propelling effect on the medium flowing through the passage will be kept from dropping as the flow through the passage continues, each passage having a cross-sectional area at the outlet portion which is smaller than of the cross-sectional area of the passage at the inlet portion, and the outer ends of the blades having a convex form on the leading sides thereof while the rear sides of the blades are substantially straight.

ALEXANDER GARVE. 

